Wikipedia:Reference desk/Archives/Science/2018 April 12

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April 12

peanut butter

No medical advice allowed. ←Baseball Bugs What's up, Doc? carrots→ 20:22, 12 April 2018 (UTC)
The following discussion has been closed. Please do not modify it.
I wonder if taking a multivitamin with peanut butter will inhibit absorption of the vitamins since it is so thick and will get stuck in it, is this accurate? I chew up the multivitamin.--User777123 (talk) 20:52, 11 April 2018 (UTC) I'm sorry, but we're not allowed to provide medical advice. You will have to read the material packaged with the drug and/or talk to a pharmacist or doctor about its interactions with food and what is best for you. Matt Deres (talk) 21:04, 11 April 2018 (UTC) As food passes through the digestive tract it becomes finely divided and mixed. Seeds are the obvious exception; they usually pass through the tract unbroken. So when medication is mixed with a semi-solid such as peanut butter, mashed potato, jam etc., the medication can be absorbed after the semi-solid has become mixed uniformly with the other stomach contents. Dolphin (t) 21:24, 11 April 2018 (UTC) Multivitamins, except some specific preparations for people with various conditions, are generally not regulated as "drugs" in most countries, but as "supplements". I don't know if this means they still fall under the "medical advice" criterion. --47.146.63.87 (talk) 22:59, 11 April 2018 (UTC) The question does not constitute a request for medical advice. Dolphin (t) 04:51, 12 April 2018 (UTC) They are asking about the efficacy of vitamins that they themselves are taking. They're not asking about what wine pairs well with fish; they're asking about the healthfulness of materials they're ingesting. At best, we should answer generically, but they've made it clear that they're asking regarding their own health. Matt Deres (talk) 18:30, 12 April 2018 (UTC) You're right. ←Baseball Bugs What's up, Doc? carrots→ 20:22, 12 April 2018 (UTC) In general, the function of your digestive system is to break up food and absorb it. As long as you have a regularly functioning one, it's pretty good at its job. Ingested substances are thoroughly broken up mechanically as well as chemically. By the time they leave your stomach they're all mixed up into goopy chyme. Lipids like the fat and oil in peanut butter are then broken up even more by bile, to facilitate absorption. Lipid-soluble substances such as Vitamin A actually need to be dissolved in lipid to get absorbed into your body. As long as you're a normally healthy person taking a typical multivitamin supplement, I wouldn't worry; just follow any packaging directions, like "take with food". If you have or think you have a medical condition, or the vitamin has been prescribed, consult a medical professional. --47.146.63.87 (talk) 22:59, 11 April 2018 (UTC)

Satellite eclipsed by satellite?

Are the signals to/from satellites in geostationary orbit ever blocked by other satellites in low earth orbit? If not by small ones, what about by something as large as the International Space Station?    → Michael J Ⓣ Ⓒ Ⓜ 01:02, 12 April 2018 (UTC)

My guess is no, and also I can find no mention of blocking by low earth objects in literature on satellite interference. Consider that the low earth objects are moving at velocities of kilometers per second compared geosynchronous satellites. Geosynchronous satellites generally use super-high frequency radio waves, which do require line-of-site to their receiver, but the papers I find on low-earth-orbit objects interfering with geosynchronous ones are talking about signals interfering with each other. Someguy1221 (talk) 02:51, 12 April 2018 (UTC)

The orbital speed of the ISS is given here as 17,239.2 mph (as its height isn't constant, I suspect they mean the mean orbital speed, but it won't vary much), which is equivalent to 7,706.6 m/s or 25,284 ft/s. According to Wikipedia the thing is 108.5 m or 356 feet wide; therefore in 1 second it will move 7706.6/108.5 = 25284/356 = 71.02 times its own width. It won't eclipse something else for longer than about 14 milliseconds. --69.159.62.113 (talk) 03:05, 12 April 2018 (UTC)

Short wavelength radio waves generally require a line-of-sight to the receiver because short wavelengths don't bend very well, but as any wave they bend at least somewhat. So diffraction helps. Without using exact numbers, which is hard given the irregular shape of the eclipsing satellite, we can estimate that when the distance from the eclipsing satellite to the receiver divided by the size of the eclipsing satellite is much larger than the size of the eclipsing satellite divided by the wavelength of the radio signal, the eclipsing satellite will have negligible influence on the received signal. For your typical SHF radio signal and your typical LEO satellite, the numbers will be of the order 100,000 and 100, respectively, so there will be no interference. The ISS is bigger, but rather sparse. It's 100 metres in size, but the width of individual modules is just a few metres. PiusImpavidus (talk) 09:30, 12 April 2018 (UTC)

Yes, space is huge. You just won't believe how vastly, hugely, mind-bogglingly big it is. Our puny ape intuition isn't designed for it. Observe the picture. Geostationary orbit is the outermost circle. The ISS orbit is the innermost one. No, look closer. That one. --47.146.63.87 (talk) 17:18, 12 April 2018 (UTC)

If space is so huge, how come chiselers have been renting it out for $2 million a year or more for the past two decades? [1] Space is finite -- this society's penchant for racketeering and rent-seeking is what truly knows no bounds. Wnt (talk) 03:26, 13 April 2018 (UTC)

I say nothing as to the suitability of current regulatory regimes, but the problem is things in space are also going very very fast. And while space is big, for satellites there are a limited number of useful orbits, given necessary properties like the orbital period, area of coverage on Earth, etc. for a given satellite. If two satellites collide, you now have an uncontrollable blizzard of debris hurtling along its orbital path at speeds faster than a bullet fired here on Earth. There is some fear this could happen and wreck a large portion of satellites currently in orbit, and possibly even make spaceflight difficult or impossible for some time.

Also, cool science fact, it's not known at present whether the universe is finite. It could very well be infinitely large, and many cosmologists think this is the case. This is mostly of intellectual curiosity because we'll never be able to interact with anything outside the (enormous but finite) observable universe. --47.146.63.87 (talk) 07:42, 13 April 2018 (UTC)

• GEO is huge, but the RF spectrum is not. There is no particular regulation prohibiting you from placing a satellite in GEO: you won't smack into another satellite (usually). However, there are regulations against transmitting in the RF in a manner that will interfere with another satellite. To a first approximation, the rules are associated with 2-degree "slots" along the GEO: that's because an economically-sized dish on the ground can focus on a slot and therefore avoid "seeing" the slots next door on either side. If another satellite were placed within two degrees and was using the same RF bandwidth, all of the millions of deployed dishes of this economical size would become unusable. -Arch dude (talk) 18:17, 14 April 2018 (UTC)

• The GEO satellite is illuminating the Ku-band antenna on your roof. The shadow of an LEO satellite on will occlude a very small part of your dish for a very brief time, so it's effectively negligible. To a first approximation the shadow moves at the velocity of the LEO satellite, which is about 7 km/s, or 7 times faster than the bullet from a high-powered rifle. For a 1-meter dish, the shadow crosses in about 140 microseconds, worst case. Consider OneWeb as an example of the new LEO constellations. A satellite crosses your sky every 3 minutes along its orbit, and an orbits sweeps east-to-west across your sky every 45 minutes. The liklihood that an orbit is between you and your GEO satellite during the 140 microseconds that a satellite in the orbit is between you and the GEO is very roughly 140/180,000,000. All of this is for a LEO satellite with a 1-meter cross section in the occluding direction. -Arch dude (talk) 04:40, 13 April 2018 (UTC)

• Geosynchronous orbit is six earth radii away. LEO is a few hundred miles. Satellite have small antennae, so their transmitted patch is large. A satellite in LEO will occlude some of the transmitted signal, but only a tiny quantity. Even if the LEO satellite passes over the ground receiver, that's affecting only one receiver, for a very short time, and not even obscuring the entire signal. Andy Dingley (talk) 11:09, 13 April 2018 (UTC)

Sugar concentration

Inspired by the fact that the sperm is sticky due to presence of sugar, but reportedly not sweet. So are substances with low sugar concentration/amount slightly adhesive, but not detectably sweet? Or there are actually both? 212.180.235.46 (talk) 08:37, 12 April 2018 (UTC)

I think you mean semen not sperm. Nil Einne (talk) 10:42, 12 April 2018 (UTC)

As water with sucrose sugar is tasting sweet long before it becomes sticky, if sperm (=semen) is not sweet I suppose that 1) it is not sticky because of sugar, or 2) that the involved sugar is not sweet, (e.g. lactose is not sweet, I think). 194.174.76.21 (talk) 11:28, 12 April 2018 (UTC) Marco Pagliero Berlin

The main sugar in semen is fractose, and the concentration is low - between 2mg per ml and 5 mg per ml. There are plenty of other things, including citiric acid, to hide the sweetness. Wymspen (talk) 11:39, 12 April 2018 (UTC)

From wikt:sperm: "2: (uncountable) Semen; the generative substance of male animals." If anything this meaning is earlier than that of the cells (not that that proves anything on its own, of course). AndrewWTaylor (talk) 12:07, 12 April 2018 (UTC)

The words "semen" and "sperm" both mean "seed" - which is also another synonym. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:48, 12 April 2018 (UTC)

It isn't sticky because of sugar, but because of mucoproteins. --Jayron32 13:55, 12 April 2018 (UTC)

Well, per mucoprotein it contains polysaccharides which are basically sugar. This confirms it also contains fructose. 212.180.235.46 (talk) 14:19, 12 April 2018 (UTC)

No, that's like saying an apple and an elephant are basically the same thing because they are both made of cells. Polysaccharides are not sugars, under the normal understanding; lots of things are (or contain) polysaccharide chains, but are not considered sugars, like cellulose and starch and glycogen, and the like. Mucoproteins are not sugars. --Jayron32 15:09, 12 April 2018 (UTC)

Also, said proteins are gradually broken down by prostate-specific antigen, to allow the sperm to move towards the uterus. --47.146.63.87 (talk) 17:27, 12 April 2018 (UTC)